This invention relates generally to nuclear reactors, and more particularly to systems and methods stabilizing voltage regulators in nuclear reactor recirculation systems.
A reactor pressure vessel (RPV) of a boiling water reactor (BWR) has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide typically is spaced above a core plate within the RPV. A core shroud surrounds the core and is supported by a shroud support structure. Particularly, the shroud has a generally cylindrical shape and surrounds both the core plate and the top guide. There is a space or annulus located between the cylindrical reactor pressure vessel and the cylindrically shaped shroud.
The core of the reactor includes an array of fuel bundles with square cross section. The fuel bundles are supported from below by a fuel support. Each fuel support supports a group of four fuel bundles. The heat generated in the core can be decreased by inserting control rods into the core, and the generated heat can be increased by retracting control rods from the core. In some known BWR""s, the control rods have a cruciform cross section with blades that can be inserted between the fuel bundles of a group of four.
Historically, reactors were designed to operate at a thermal power output higher than the licensed rated thermal power level. To meet regulatory licensing guidelines, reactors are operated at a maximum thermal power output less than the maximum thermal power output the reactor is capable of achieving. These original design bases include large conservative margins factored into the design. After years of operation, it has been found that nuclear reactors can be safely operated at thermal power output levels higher than originally licensed. It has also been determined that changes to operating parameters and/or equipment modifications will permit safe operation of a reactor at significantly higher maximum thermal power output (up to and above 120% of original licensed power).
Reactor plant systems, such as, the reactor recirculation system are evaluated to ensure their capabilities can support the reactor plant""s operation at the higher power output levels. Where appropriate, changes are made to such systems to improve their performance.
In one aspect, a method of regulating an output voltage of a boiling water reactor nuclear reactor plant recirculation system motor generator is provided. The method includes sensing an alternator output voltage and transmitting an alternator output voltage signal to a voltage regulator circuit, sensing an alternator speed and transmitting an alternator speed signal to the voltage regulator circuit, comparing the alternator output voltage signal to the alternator speed signal with a volts per hertz divider network electrically coupled to the alternator output voltage sensing circuit and the alternator speed sensing device, adjusting a capacitive reactance of the voltage regulator with a lead compensation circuit electrically coupled in series with the volts per hertz divider network, and adjusting a current in a control winding of a saturable reactor.
In another aspect, a voltage regulator for a boiling water reactor nuclear reactor plant recirculation system is provided. The regulator includes a variable frequency alternator, an alternator output voltage sensing circuit electrically coupled to a control circuit, an alternator speed sensing device electrically coupled to the control circuit, a volts per hertz divider network electrically coupled to the alternator output voltage sensing circuit and the alternator speed sensing device, a lead compensation circuit electrically coupled in series with the volts per hertz divider network, and a saturable reactor including a control winding electrically coupled to the volts per hertz divider network output, and a secondary winding electrically coupled to said alternator exciter.